A variety of thermoelectric transducers are known in the art for converting electric current into thermal energy, and vice versa. In general, when an electric current passes through such a transducer, a temperature differential is produced across opposite sides or portions thereof. This phenomenon is known as the Peltier effect. Conversely, when two sides or portions of a thermoelectric transducer have different temperatures, the transducer produces an electric current. This opposite or reverse phenomenon is known as the Seebeck effect. Thus, a thermoelectric transducer can be used to produce thermal cooling (or heating) or electric current.
In practice, thermoelectric transducers are frequently used to provide cooling for heat-sensitive devices or systems. For example, the "cold side" of Peltier transducers (typically semiconductor devices implemented in integrated circuit packages) are commonly connected to other types of electronics and computer devices, and are driven with electric current to produce cooling and thereby reduce operating temperatures. In the opposite direction, thermoelectric devices have long been used to sense temperature differences in various systems. For example, a thermoelectric thermocouple is commonly employed in the control system for traditional natural gas equipment to sense the heat produced by a pilot light, and to provide a current signal indicative thereof. In this manner, the control system can ensure the pilot light is present and burning before natural gas is released.
On a much more limited basis, thermoelectric transducers have also been used as thermoelectric power generators for producing usable electric power from heat. For example, thermocouple thermopiles--often constructed of cascaded bimetallic thermocouples--have been used to convert heat collected from the sun into electric power (this should be distinguished from converting solar light energy into electric power using photovoltaic devices or "solar cells"). However, the thermopiles cannot produce electric power at times when heat from the sun cannot be collected, such as at night and during adverse weather conditions. Accordingly, the electric power produced by these thermopiles must be stored, such as in batteries, in order to be available at times when electric power cannot be so produced on demand. Thermopiles have also been used to convert heat produced by radioactive isotopes ("radioisotopes") into electric power, but this approach has not been commercially implemented, presumably due to the impractical nature of using radioisotopes and related environmental and health issues.
Apparently because of the high temperatures generally required by known thermoelectric power generators to produce desired amounts of electric power--typically on the order of several hundred or even several thousand degrees Fahrenheit--and because semiconductor devices are generally unsuitable for such high temperature applications, the advantages and additional options provided by semiconductor technology have not been exploited in the field of thermoelectric power generation.